Mandibular changes associated with maxillary impaction
and molar intrusion
Sondos Abuzinada, Fahad Alsulaimani
King Abdulaziz University, Jeddah, Saudi Arabia Email: [email protected]
Received 29 October 2013; revised 29 November 2013; accepted 11 December 2013
Copyright © 2013 Sondos Abuzinada, Fahad Alsulaimani. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
We report a case series of ten patients who presented with anterior open bite. The initial evaluation in- cluded clinical pictures, lateral cephalometric radio- graphs and dental casts. They were assessed accord- ing to the severity of the open bite and the cause (skeletal or dental). They all underwent orthodontic treatment as an initial step. Five patients with dental open bite underwent molar intrusion using titanium screws and five patients underwent maxillary Le Fort I impaction. We report the mandibular changes asso- ciated with these different treatment modalities with improved esthetics.
Keywords:Maxillary Impaction; Molar Intrusion; Open
Bite; Le Fort I; Titanium Screws
1. INTRODUCTION
Vertical Maxillary Excess (VME) is one of the most fre- quently encountered dentofacial deformities. This can result in an anterior open bite or an unesthetic gummy smile. The correction of vertical problems with or with- out open bite usually includes maxillary Le Fort I im- paction [1]. On the other hand, the correction of an open bite can be managed orthodontically by molar intrusion [2].
The mandible in such cases is either retrognathic or within normal position and will respond to the superior positioning of the maxilla by autorotation. In some cases this autorotation will add the need to perform mandibular surgery to either advance or setback the mandible and is case-dependent [3,4]. With the mandibular autorotation, the chin position advances. This can be estimated in the presurgical prediction, but requires great accuracy as this will decide if only maxillary Le Fort I impaction will need or two jaw surgeries. Some studies have been made
for predicting mandibular autorotation following manxil- lary impaction [5,6]. However, controversies in locating the center of mandibular autorotation revealed the inabil- ity to accurately predict the final position of the mandible after maxillary impaction [6-8]. On the other hand, it has been documented that the mandible will move forward following maxillary impaction with a chin advancement in 1:1 ratio [9].
Molar intrusion is used to manage an open bite. A number of patients do not wish to perform orthognathic surgery because of the involved risk. For such patients, various alternatives can be used, including multibrackets in conjunction with high-pull headgear therapy (2), mul- tiple-loop edgewise arch wire (MEAW) therapy (3), re- versed curve nickel-titanium wire with intermaxillary elastics (4) and extraction therapy (5). These treatment modalities can achieve acceptable overbite and interin- cisal relationship which also guide the mandible and chin into a new position leading to a more esthetic appearance [10].
In this article we present a series of cases. Some un- derwent orthodontic molar intrusion and others under- went maxillary Le Fort I impaction. We compare the changes in mandibular position and the resulting esthetic improvement for each technique.
2. PATIENTS AND METHODS
tients diagnosed with vertical maxillary excess and ret- rognathia included presurgical orthodontic treatment (leveling, alignment and decompensation) followed by maxillary Le fort l osteotomy with impaction and fixa- tion using four 1.5 mm miniplates. This was followed by an advancement genioplasty according to patients need. However, patients diagnosed with anterior open bite without vertical maxillary excess underwent orthodontic treatment. The cause of the anterior open bite in these cases was suggested to have been extrusion of both upper molars, based on cephalometric readings, therefore, the plan was to intrude both upper molars using implanted titanium screws to deliver the force.
3. ORTHODONTIC TREATMENT FOR
OPEN BITE
Bonding and banding of all teeth, using 0.022-inch slot, preadjusted edgewise appliances were placed in both arches (Victory SeriesTM, Roth Rx, 3M Unitek, Monrovia, CA, USA) and leveling and aligning phase using pro- gressive sequencing of arch wires. was performed. Cor- rection of the two-step occlusal plane was done during the leveling and aligning phase by extrusion of anterior teeth. Once a heavy stainless steel arch wire (0.019" × 0.025") was reached, Titanium screws (1.6-mm diameter, 8-mm length; (RMO Co. Ltd., Denver, Colorado, USA) were inserted bilaterally in the alveolar bone of the maxilla through the buccal mucosa between the second bicuspid and the first molar from both the labial and palatal area in
the same visit under local anesthesia was administered. Analgesics were prescribed to the patients for 3 days after the implantation. One week after implantation of the ti- tanium screws, intrusion of posterior teeth began using elastic chains. The total active treatment period was 19 months. The implant screw anchorage was stable for the entire duration of the treatment, and the screws were removed during the retention phase. Another cepha- lometric radiograph was taken upon completion of or- thodontic treatment and Stiner analysis was repeated.
4. RESULTS
Five patients with anterior open bite and VME under- went orthognathic surgery (Le fort I maxillary impaction with more posterior impaction. An advancement genio- plasty was also done in three patients. Five patients with anterior open bite underwent orthodontic treatment only. The results of the cephalometric analysis are listed in (Table 1). The counter clockwise rotation of mandibular
plane improved the chin position in three patients who underwent orthodontic treatment (Figure 1) and in all
five patients who underwent maxillary impaction this was demonstrated by a decrease in mandibular plane angle and an increase in SNA (Figure 2). Two patients
[image:2.595.55.545.490.735.2]who underwent orthodontic treatment for closure of an- terior open bite showed clockwise rotation of the man- dibular plane with an increase in mandibular plane angle and a minimal decrease in SNB. However, all patients showed improvement in facial profile and function. The
Table 1. Cephalometric values for patients who underwent molar intrusion and patients who underwent maxillary impaction (DX: diagnosis; DOB: dental anterior open bite).
Patient number Dx Incisal show at rest Open bite (mm) Man plane Occlusal plane Point B to N┴FH SNB
1 DOB 3 mm 5 mm 30 25 14 8 0 2 70 73
2 DOB 3 mm 4 mm 47 45 16 20 10 10 75 72
3 DOB 2 4 mm 38 36 17 16 10 9 85 84
4 DOB 3 5 mm 35 33 15 17 6 6 82 80
5 DOB 4 mm 5 mm 39 36 18 15 6 8 81 81
6 VME 5 mm 4 mm 52 50 19 18 13 9 80 84
7 VME 7 mm 4 mm 49 44 17 14 10 10 72 73
8 VME 8 mm - 42 33 13 9 55 52 80 85
9 VME 6 mm 3 mm 35 28 13 11 11 7 69 72
[image:3.595.81.520.87.268.2]
(a) (b) (c)
Figure 1. (a) Lateral cephalometric radiograph before molar intrusion; (b) Lateral cephalometric radiograph after molar intrusion; (c) Lateral cephalometric tracing before molar intrusion (blue) after molar intrusion (red).
(a) (b)
Figure 2. (a) Lateral cephalometric radiograph before maxillary impaction; (b) Lateral cephalometric radiograph after maxillary impaction.
retrognathic chin and convex profiles were corrected, resulting in a straight profile. The facial proportions were also improved due to of the decrease in the lower facial height. The strain in the circumoral musculature during lip closure was improved.
5. DISCUSSION
Many studies in the literature mention the esthetic effects of maxillary Le Fort I impaction related to the resulting mandibular counter clockwise rotation [1,3,4]. However, not much is mentioned regarding the effect of molar in- trusion on the mandibular plane angle and the resulting esthetic effect. The results of our study showed that mo- lar intrusion used to close anterior open bite gives some esthetic results as seen in maxillary Le Fort I impaction. However, this was not noted in all orthodontically treated
cases with anterior open bite.
[image:3.595.141.459.308.503.2]open bite closure showed improved esthetics, however, not all patients showed mandibular counter clockwise rotation as seen in Le Fort I impaction. Some patients showed clockwise mandibular rotation. This was ex- plained by the orthodontic treatment, since two of the patients have constricted maxilla. Expansion appliance such as Quad-Helix was used to expand the maxillary teeth. It is well documented with expansion clock wise rotation of the mandibular plane which has taken place due to extrusion of the palatal cusp. The clock wise rota- tion point pog will also rotate backward. The difference between pre and post treatment was in average 2 degrees which could be due to the occlusal plane measured at functional occlusion with no anterior teeth contacting a measurement error that was possible. The most important is the reduction of the mandibular plane which showed a counter clock wise rotation in all the patients with es- thetic improvement.
On the other hand, the skeletal improvement is poor due to failure to establish absolute anchorage during mo- lar intrusion. To obtain absolute anchorage, several de- vises have been used such as dental implant [11-14], screws [15,16] and miniplates [17,18]. The advantages of these devices are by providing absolute anchorage dif- ferent teeth movement without the need for patient’s co- operation. Several reports have been reported on the use of screw for anchorage in teeth movement, intrusion or retraction of anterior teeth [10,11], and protraction of posterior teeth in the mandible. In addition, few papers have reported the use of titanium screws for orthodontic anchorage to intrude upper and/or lower molars of an adult patient with severe skeletal anterior open bite.
The mandible will follow any changes in occlusion resulting from maxillary impaction or molar intrusion. The noted changes in mandibular and chin position were quite variable and less predictable following molar intru- sion, however, the improved esthetics can be appreciated in all patients. Future standardized studies will help us make accurate predictions following molar intrusion or maxillary impaction.
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